Flow cytometry has become a integral and essential technological tool in modern biomedical research today. As instruments have become more sophisticated, the uses of flow cytometry have expanded into a variety of research interests. In addition to the classic fields of immunology and hematology involving AIDS and cancer research, flow cytometry is now used in such areas as developmental biology and molecular studies of gene regulation. We propose to purchase a Becton-Dickinson FACStarPlus Dual Laser Flow Cytometer with a DEC MicroVAX II (VAX Station 3500). This instrument will be part of the Flow Cytometry Core Facility of the Comprehensive Cancer Center (CCC) of Columbia University. This instrument will be the centerpiece of the facility which will provide badly needed state-of-the- art flow cytometry for scientists at Columbia and which will result in many new avenues of research. While priority will be given to the over 150 members of the CCC the instrument will be available to the Columbia scientific community as usage permits. The CCC Flow Cytometry Facility, in addition to providing flow cytometry, will act as a central resource of information, helping researchers at Columbia to design and develop experiments using flow cytometry and to extract the most information from the resulting data.